Hop (Humulus lupulus L.) is a perennial herbaceous climbing plant from the Cannabaceae family. It is native to Europe, western Asia, and North America. Only female plants are grown in hop fields, while male ones are not desired, to prevent the pollination of the female plants. Male hop plants have no commercial value other than for use in breeding programs to create new varieties. The life expectancy of hop plant is from ten to twenty years and depends mainly on the growing conditions, variety, and agricultural practices. The hop plant includes above-ground and below-ground vegetative parts. Normally, the above-ground parts of the plant die back to ground level every winter, but below-ground parts (or rootstock) are perennial. The commercial value of hops lies in the lupuline glands that contain resins (α-acid, β-acid) which give beer its bitterness and essential oils which contribute to beer flavor. New hop varieties are evaluated in terms of their growing characteristics, hop cone yields, disease resistance, hop resins, and essential oil components.
The flowers (cones) of the female hop plant, Humulus lupulus L., are used in the making of beverages, especially beer, as a flavoring and processing component. Hops contribute towards the bitterness and aroma in beer as well as foam quality, flavor, and taste stability. Various hop varieties have various special uses in the beer brewing industry. Aroma hops are used to impart flavors by virtue of the distinct profiles of their essential oils and terpene alcohols, among other compounds, as well as to supply bitter flavors based on specific contents of bitter acids, namely, terpenophenolics, mostly humulones.